With a software update released last fall, Apple enabled the HomePods to be used as the default audio output for Apple TV. This allowed all audio from the Apple TV to be sent to the HomePod speakers, with a simulated Dolby Atmos soundscape.
With the new Apple TV 4K, tvOS supports HDMI ARC and eARC for the first time. This means that all audio from all input sources can now be output through the HomePod speakers, provided the user has an ARC compatible TV. What eARC/ARC allows is for an accessory connected via HDMI to be the global speaker output for the TV. This means that all audio from game consoles, cable boxes and the like can be routed through the Apple TV output, with the sound being transmitted through the HomePods. With ARC support, the HomePod can be used to output all audio sources on the actual TV, not just when using the Apple TV itself. This makes the Apple TV + HomePod combination a much more compelling option for the TV's primary speaker system in the living room. For this to work, users need a second-generation Apple TV 4K, HomePod speakers, and a compatible TV that supports HDMI ARC or eARC.

Apple TV 4K: The HomePod mini is left out
Complete instructions can be found on the support page from Apple. Interestingly, the Audio Return Channel feature is marked as "beta" in the Apple TV interface. The biggest catch, however, is that all standard audio features on Apple TV only work with the large HomePod. That is, the HomePod that was discontinued some time ago. Whether the HomePod mini will also be supported at some point remains to be seen. The inclusion of ARC in the latest generation of Apple TV shows that Apple had bigger ambitions for the HomePod as a wireless living room speaker before the product was abruptly discontinued. Apple's long-term vision for the living room remains unclear. A report from Bloomberg earlier this year suggested that Apple was considering a next-generation set-top box with speakers and a FaceTime camera. (Image: Apple)